SubPopulations and InteRmediate Outcome Measures In COPD Study (SPIROMICS) contractors will design and conduct a clinical research study with extensive subject phenotyping and molecular fingerprinting to identify subpopulations of patients with chronic obstructive pulmonary disease (COPD) and to identify and validate surrogate markers of disease severity which will be useful as intermediate outcome measures for clinical trials. Research subjects will be enrolled, phenotyped, and followed at approximately six Clinical Centers (CCs). A Genomics and Informatics Center (GIC) will have primary responsibility for developing a scientific plan for achieving study aims; analyzing phenotypic and high-throughput molecular data; operating a repository of biospecimens; developing bioinformatic resources; data management; providing overall management and oversight of the study; and disseminating study results. The Radiology Center will have primary responsibility for standardizing imaging methods at the Clinical Centers; establishing a repository of CT image data; assessing and assuring quality of CT images; and analyzing CT images to obtain quantitative measures that may indicate the presence and/or severity of COPD or other lung diseases.